Firearm projectile with bonded rear core

ABSTRACT

The present invention is a controlled expansion projectile ( 20 ) having a bonded rear core and includes a metal jacket ( 22 ), a dense core ( 24 ), and a tip ( 26 ). Metal jacket ( 22 ) includes a nose portion ( 28 ), a middle portion ( 30 ), and a heel portion ( 32 ). Nose portion ( 28 ) includes a front cavity ( 34 ) and heel portion ( 32 ) includes a rear cavity ( 36 ) defined by sidewalls ( 40 ), an open end ( 42 ), and heel ( 44 ). Dense core ( 24 ) is typically formed from lead but may be formed from lead compounds or other heavy metals. Dense core ( 24 ) may be enclosed in rear cavity ( 36 ) using a closure disc ( 48 ) joined with heel ( 44 ) to seal open end ( 42 ). Dense core ( 24 ) is joined with sidewalls ( 40 ) thereby forming a bond ( 52 ). Bond ( 52 ) may be a metallurgical bond ( 54 ), a mechanical bond ( 56 ), or an adhesive bond ( 58 ). Tip ( 26 ) is at least partially inserted in front cavity ( 34 ). Sidewalls ( 40 ) of rear cavity ( 36 ) are softened during either a metallurgical bonding process or other processes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to firearm projectiles. In particular, the present invention is directed to a firearm projectile with a bonded rear core.

2. Description of the Related Art

Firearm projectiles used for hunting are generally small caliber, i.e., less than 0.50 caliber. They generally have a hollow point or soft metal nose portion to increase expansion of the projectile upon impact with animal tissue in order to achieve increased energy adsorption within the target animal's body. Many hunting projectiles, specifically lead-tipped or hollow point projectiles have a significant drawback for use in hunting applications in that they tend to upset and expand greatly, even to the point of fragmentation, within a short penetration distance and are thus not suitable for deep penetration. This is particularly true where the projectile hits a bone during passage into the animal. Hunters often aim for the shoulder area of the target animal in order to minimize the chance of the animal escaping after it has been shot and because the vital organs of the animal are in the same general area of the animal as the shoulder. As a result, the projectile often strikes bone.

Expansion of the projectile is desirable to slow the projectile and transfer more energy to the target during passage through soft animal tissue. If the projectile does not expand significantly and does not hit a bone or vital organ, it may pass through the animal without killing the animal or stopping the animal. For the projectile to successfully pass through animal bone and still do damage to vital organs, it is necessary that the projectile have density, sufficient structural integrity, and retained weight.

One prior art firearm projectile used for hunting applications discloses a unitary metal body having a generally H-shaped longitudinal cross section including an empty hollow point in front and a rear cavity filled with a dense core formed from a material such as lead. The rear cavity is closed by a disk to seal the dense core from the environment. Because the rear cavity is filled with a dense core, the majority of the weight of this projectile is contained in the rear portion. As a result, this projectile has good weight retention because the projectile does not lose a significant part of its weight even if the petals in the front break off during penetration of the target.

This projectile tends to bulge due to the forward inertia and kinetic energy of the heavy dense core during the rapid deceleration upon impact. Specifically, the forward portion of the sidewalls of the rear cavity of the projectile tends to bulge. Advantageously, the bulge helps in making a larger diameter wound channel.

However, the dense core of this projectile is not bonded to the sidewalls of the rear cavity. Rather, the dense core is pressure fit within the rear cavity. As a result, this projectile has been found to break apart when it hits heavy bones at or near muzzle velocity. Failure has been found to develop at the bulge discussed above. When the projectile breaks apart, the dense core is separated from the jacket of the projectile thereby undermining its overall performance. In addition, because many dense cores contain lead, it is desired that the integrity of the projectile be maintained to prevent contamination of animal tissue due to lead exposure.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is controlled expansion projectile, including a unitary metal jacket including nose, middle, and heel portions. The nose portion includes a front cavity and the heel portion includes a rear cavity having sidewalls. The nose and heel portions are joined to one another via the middle portion. A dense core is contained within the rear cavity and bonded to the sidewalls. A tip is at least partially inserted in the front cavity.

Another aspect of the present invention is a method of fabricating a controlled expansion projectile, which includes the following steps: providing a unitary metal jacket including nose, middle, and heel portions, the nose portion including a front cavity and the heel portion including rear cavity having sidewalls, the nose and heel portions joined to one another via the middle portion; filling the rear cavity with a dense core; bonding the dense core to the sidewalls of the rear cavity; softening the metal jacket adjacent the rear cavity; and inserting a tip in the front cavity.

Still another aspect of the present invention is a controlled expansion projectile, which includes a unitary metal jacket including nose, middle, and heel portions. The nose portion includes a front cavity and the heel portion includes a rear cavity having sidewalls. The nose and heel portions are joined to one another via the middle portion. A dense core is contained within the rear cavity. The controlled expansion projectile also includes means for bonding the dense core to the sidewalls and means for increasing a ballistic coefficient of the projectile.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show a form of the invention that is presently preferred. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a cross section of a controlled expansion projectile according to one embodiment of the present invention taken along its longitudinal axis;

FIG. 2A is a cross section taken along line 2-2 of FIG. 1 of a controlled expansion projectile having a metallurgical bond according to one embodiment of the present invention;

FIG. 2B is a cross section taken along line 2-2 of FIG. 1 of a controlled expansion projectile having a mechanical bond according to one embodiment of the present invention;

FIG. 2C is a cross section taken along line 2-2 of FIG. 1 of a controlled expansion projectile having an adhesive bond according to one embodiment of the present invention; and

FIG. 3 is a side view and partial cross section of the controlled expansion projectile of FIG. 1 after being fired and striking an object.

DETAILED DESCRIPTION

Referring now to the drawings in which like reference numerals indicate like parts, and in particular, to FIG. 1, the present invention is a controlled expansion projectile 20 having a metal jacket 22, a dense core 24, and a tip 26.

Metal jacket 22 includes a nose portion 28, a middle portion 30, and a heel portion 32. Metal jacket 22 is typically a substantially cylindrical body formed around a longitudinal axis 33. Metal jacket 22 is generally formed of a unitary construction having an H-shaped cross-section as taught in U.S. Pat. No. 3,003,420, and fabricated from a copper alloy as taught in U.S. Pat. No. 5,385,101, both of which are hereby incorporated by reference as if disclosed herein in their entirety. Metal jacket 22 may be fabricated from alloy CDA 210 or similar, which is commonly used in commercially available bullet jackets. Alternatively, metal jacket 22 may be fabricated from a copper-zinc alloy such as CDA 220 or CDA 226, or a pure CDA 100 series metal. Of course, in other embodiments, other materials and other configurations may be used. In addition, a multi-piece construction is also contemplated for use as part of the present invention.

Nose portion 28 includes a front cavity 34 and heel portion 32 includes a rear cavity 36 defined by sidewalls 40, an open end 42, and heel 44. Nose portion 28 and heel portion 32 are joined to one another via middle portion 30. Middle portion 30 is typically formed from a solid layer of the same material used to form metal jacket 22 and serves as a partition between front cavity 34 and rear cavity 36.

Dense core 24 is typically formed from lead but may be formed from lead compounds or other heavy metals as taught in U.S. Pat. No. 5,127,332, which is hereby incorporated by reference as if disclosed herein in its entirety. Dense core 24 may be formed from a lead-antimony alloy. Bullet geometry and upset tendencies typically dictate which specific lead-antimony (or other lead alloy) to use in dense core 24 depending on desired performance characteristics. In one embodiment, dense core 24 may be enclosed in rear cavity 36 using a closure disc 48 joined with heel 44 to seal open end 42 as taught in U.S. Pat. No. 5,333,552, which is hereby incorporated by reference as if disclosed herein in its entirety. Alternatively, a unitary metal jacket having a closed heel (not shown) may be formed around dense core 24 thereby enclosing the dense core within rear cavity 36.

Tip 26 is at least partially inserted in front cavity 34. Tip 26 is typically formed from a polycarbonate or polypropylene material and is shaped to a point. Inclusion of tip 26 helps lower the overall form factor (i) of controlled expansion projectile 20 thereby increasing the ballistic coefficient (C) (C=w/id², where d=diameter of projectile and W=weight of the projectile). Alternative materials may be used for tip 26 and/or the tip may be integral to metal jacket 22 providing the alternative materials or alternative construction increase the ballistic coefficient. Other than tip 26, front cavity 34 is typically empty and does not include any dense materials such as lead.

Dense core 24 is joined with sidewalls 40 thereby forming a bond 52. Bond 52 helps prevent dense core 24 from separating from metal jacket 22 when the projectile strikes an object. Referring now to FIG. 2A, bond 52 may be a metallurgical bond 54 formed between sidewalls 40 and dense core 24. Typically, metallurgical bond 54 is formed during a process in which dense core 24 is brought to a molten state to bond it to sidewalls 40. This process also serves to soften metal jacket 22 adjacent rear cavity 36 along a thickened area 55 of sidewalls 40 through annealing. Referring now to FIG. 2B, bond 52 may be a mechanical bond 56 between sidewalls 40 and dense core 24. Examples of mechanical bonds include crimps, stakes, reverse tapers, interfering surface finishes, threads, or similar methods. Referring now to FIG. 2C, bond 52 may be an adhesive bond 58 between sidewalls 40 and dense core 24. Various adhesives such as glues or epoxies may be utilized to form a permanent adhesive bond 58 between dense core 24 and sidewalls 40. For embodiments where bond 52 is not a metallurgical bond, metal jacket 22 adjacent rear cavity 36 may also be softened using an annealing process prior to forming the bond.

Another aspect of the present invention is a method of fabricating a controlled expansion projectile. First, unitary metal jacket 22 as described above is provided. Next, rear cavity 36 is filled with dense core 24. Then, dense core 24 is bonded to sidewalls 40 of rear cavity 36 thereby forming bond 52 between the dense core and sidewalls. Bond 52 may be a metallurgical, mechanical, or an adhesive bond. As dense core 24 is bonded to sidewalls 40, a portion, e.g., thickened area 55, of metal jacket 22 adjacent rear cavity 36 along bond 52 is softened. Finally, tip 26 is inserted into front cavity 34. For embodiments where bond 52 is not a metallurgical bond and depending on the material used to form metal jacket 22, an additional step of softening the metal jacket adjacent rear cavity 36 using an annealing process may also be included prior to forming the bond. Use of a metallurgical bond allows both bonding of dense core 24 to sidewalls 40 and annealing of sidewalls 40 to be accomplished during the same operation. Optionally, the method may include a further step of enclosing dense core 24 within front cavity 34 by joining closure disc 48 to heel 44 of metal jacket 22 or utilizing an alternative metal jacket that is formed around the dense core. Closure disc 48 may be joined to heel 44 using mechanical methods such as crimping or using adhesives.

Referring now to FIG. 3, in use, upon striking an object after being fired, front cavity 34 splits and peels back toward heel portion 32 thereby forming petals 60. At the same time, sidewalls 40 and dense core 24 accordion forward toward petals 60 to define a bulge portion 62. Bulge portion 62 supports petals 60 thereby preventing them from tearing away from projectile 20 during impact. As mentioned above, bond 52 between sidewalls 40 and dense core 24 prevents the dense core from separating from metal jacket 22 when the projectile strikes an object.

Projectiles designed according to the present invention offer advantages over prior art designs. Tip 26, which is positioned within front cavity 34, both of which are forward of middle portion 30, initiates the upset or expansion of projectile 20. However, after tip 26 is expelled, middle portion 30, which is formed from a solid layer of copper alloy or similar material, is exposed to the upset media. As a result, dense core 24, which often contains lead or other heavy metals, is not exposed to the media thereby preventing contamination of the media and protecting rear core from “washing,” which would reduce the overall retained weight.

The inclusion of tip 26 is advantageous because it decreases the meplat size of the projectile thereby leading to an increase in the projectile's ballistic coefficient and better downrange performance. Specifically, an increase in the ballistic coefficient increases downrange velocity, which in turn decreases the size of the velocity window for which the projectile must upset. This is beneficial over prior art designs as it increases the overall performance of the projectile over a larger range of distances from the barrel muzzle since the projectile is more aerodynamic and is losing its speed at a slower rate.

Bonding the rear cavity sidewalls and dense core provides benefits over non-bonded designs because the dense core, which often contains lead or other heavy metals, is prevented from contacting the upset media thereby preventing any of the dense core from being washed off and contaminating the media. In addition, the bonded dense core is also beneficial when the projectile strikes a hard object such as bone and the metal jacket is ruptured, because the bond between the rear cavity sidewalls and the dense core minimizes the escape of dense core pieces from the rear cavity. Typically, pieces of the dense core only escape the rear cavity where entire pieces of the metal jacket and rear cavity itself, are severed from the projectile. Because the dense core does not separate from the jacket, projectiles including a bonded dense core according to the present invention have improved weight retention over prior art designs.

Another benefit of the present invention is attributed to the softened rear cavity sidewalls of the metal jacket. A projectile according to the present invention does not try to eliminate core jacket separation by eliminating the bulging tendencies of the rear cavity. Rather, projectiles according to the present invention are designed so that the bulging tendencies are utilized in a positive way. Because the sidewalls of the rear cavity are softened during either a metallurgical bonding process or other processes, the sidewalls are more malleable and less likely to rupture. Instead, they bulge outwardly but typically remain intact. As mentioned above, even where the bulging sidewalls do rupture, the bonding of the dense core to the rear cavity sidewalls helps ensure that little or no weight will be lost due to core jacket separation. The bulging portion of the metal jacket supports the front petals during upset to ensure that they are not separated from the projectile. By keeping the petals attached, both higher weight retention is achieved and a much larger expanded diameter is possible. As a result, more energy is transferred from the projectile to its target by means of a larger wound channel.

Projectiles incorporating aspects of the present invention offer increased versatility over prior art projectiles. For example, the same .308 caliber 150 grain bullet according to the present invention may be used in a 30 caliber cartridge with a muzzle velocity of approximately 2800 fps and also used in the much faster 30 caliber cartridge with a muzzle velocity of 3300 fps. The combination of an annealed bullet jacket and bonded rear lead core allow the projectile to exhibit effective upset characteristics at a very wide range of impact velocities. The upsetting petals, in combination with the bulging of the rear core, exhibit the necessary strength to be retained to the upsetting bullet at high velocities, but in combination with the plastic tip, also the requisite softness to facilitate expansion at low velocities.

The following table provides a comparison between a projectile according to the present invention, i.e., with bonding of the dense core to the rear cavity, and a projectile according to a prior art projectile that does not include bonding of its dense core to its rear cavity. Projectile According Projectile According to the Prior Art to the Present (without bonding of Invention (with dense core to rear bonding of dense core Test cavity) to rear cavity) At muzzle velocity as shot into 20% gelatin Penetration (inches) 27-30 16-19 Expanded Diameter .400-.450 .700-.750 (inches) Retained Weight (%) 78-83  95-100 At muzzle velocity as shot into cow bone and 20% gelatin Penetration (inches) 17-20 14-17 Expanded Diameter .475-.525 .600-.650 (inches) Retained Weight (%) 70-75 78-83 At 300 yard velocity as shot into 20% gelatin Penetration (inches) 30-33 22-25 Expanded Diameter .400-.450 .575-.625 (inches) Retained Weight (%) 78-83  95-100

The results show that the projectile according to the present invention, i.e., with bonding of the dense core to the rear cavity, has a higher retained weight, an increased expanded diameter, and a decreased penetration over a prior art projectile that does not include bonding of its dense core to its rear cavity. In addition, the decreased penetration is deemed acceptable because the amount of penetration is still sufficient for most applications, e.g., hunting.

Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention. 

1. A controlled expansion projectile, comprising: a unitary metal jacket including nose, middle, and heel portions, said nose portion including a front cavity and said heel portion including rear cavity having sidewalls, said nose and heel portions joined to one another via said middle portion; a dense core contained within said rear cavity and bonded to said sidewalls; and a tip at least partially inserted in said front cavity.
 2. A projectile according to claim 1, further comprising a metallurgical bond between said sidewalls and said dense core.
 3. A projectile according to claim 1, further comprising a mechanical bond between said sidewalls and said dense core.
 4. A projectile according to claim 1, further comprising an adhesive bond between said sidewalls and said dense core.
 5. A projectile according to claim 1, wherein said dense core includes lead.
 6. A projectile according to claim 1, wherein said front cavity does not contain lead.
 7. A projectile according to claim 1, wherein said tip includes a substantially polycarbonate or polypropylene material.
 8. A projectile according to claim 1, further comprising a closure disc joined with said heel portion to enclose said dense core within said front cavity.
 9. A projectile according to claim 1, wherein said metal jacket has a substantially H-shaped axial cross section.
 10. A projectile according to claim 1, further comprising means for joining said dense core with said sidewalls.
 11. A projectile according to claim 10, wherein said means for joining prevents said dense core from separating from said metal jacket.
 12. A projectile according to claim 10, wherein said means for joining includes means for softening said metal jacket adjacent said rear cavity.
 13. A projectile according to claim 1, further comprising means for preventing said dense core from separating from said metal jacket when the projectile strikes an object.
 14. A projectile according to claim 1, further comprising means for enclosing said dense core within said front cavity.
 15. A projectile according to claim 1, further comprising means for increasing a ballistic coefficient of the projectile.
 16. A projectile according to claim 1, wherein said metal jacket is softened adjacent said rear cavity.
 17. A projectile according to claim 1, further comprising means for softening said metal jacket adjacent said rear cavity.
 18. A projectile according to claim 1, wherein upon striking an object after being fired, said front cavity peels back toward said heel portion thereby forming petals and said sidewalls and said dense core accordion forward toward said nose portion thereby defining a bulge.
 19. A projectile according to claim 18, further comprising means for supporting said petals.
 20. A projectile according to claim 19, wherein said means for supporting is said bulge.
 21. A method of fabricating a controlled expansion projectile, comprising the steps of: providing a unitary metal jacket including nose, middle, and heel portions, said nose portion including a front cavity and said heel portion including rear cavity having sidewalls, said nose and heel portions joined to one another via said middle portion; filling said rear cavity with a dense core; bonding said dense core to said sidewalls of said rear cavity; softening said metal jacket adjacent said rear cavity; and inserting a tip in said front cavity.
 22. A method according to claim 21, wherein said bonding step includes forming a metallurgical bond between said sidewalls and said dense core.
 23. A method according to claim 21, wherein said bonding step includes forming a mechanical bond between said sidewalls and said dense core.
 24. A method according to claim 21, wherein said bonding step includes forming an adhesive bond between said sidewalls and said dense core.
 25. A method according to claim 21, further comprising the step of enclosing said dense core within said front cavity.
 26. A controlled expansion projectile, comprising: a unitary metal jacket including nose, middle, and heel portions, said nose portion including a front cavity and said heel portion including rear cavity having sidewalls, said nose and heel portions joined to one another via said middle portion; a dense core contained within said rear cavity; means for bonding said dense core to said sidewalls; and means for increasing a ballistic coefficient of the projectile.
 27. A projectile according to claim 26, wherein said means for bonding includes a metallurgical bond between said sidewalls and said dense core.
 28. A projectile according to claim 26, wherein said means for bonding includes a mechanical bond between said sidewalls and said dense core.
 29. A projectile according to claim 26, wherein said means for bonding includes an adhesive bond between said sidewalls and said dense core.
 30. A projectile according to claim 26, wherein said means for increasing a ballistic coefficient of the projectile includes a tip at least partially inserted in said front cavity. 